1. Field of the Invention
The invention is directed to an improved armature for a direct current motor, in particular for a permanent-magnet-excited direct current motor.
2. Description of the Prior Art
In permanent-magnet-excited direct current or DC motors, to increase the magnetic flux in the armature body, the axial length of the permanent magnets is selected to be greater than the axial length of the armature body (German Patent Disclosure DE 199 42 903 A1, FIGS. 5 and 12). This effect is further reinforced if the armature body as additionally lengthened in the axial direction as well. By increasing the magnetic flux, the specific weight of the DC motor can be increased, or for the same motor power, a shorter axial length of the motor can be attained.
In a known DC motor (German Patent Disclosure DE 100 45 549 A1), the armature body comprises a supporting part made of resin, which is embodied in one piece with the armature shaft and has a shorter axial length than the permanent magnets, and a core, seated on the supporting part in a manner fixed against relative rotation, the core being made as a mold-cast part from a soft magnetic powder. The core has an integral outer wall of soft magnetic powder, which leaving an air gap is located opposite the permanent magnets and has approximately the same axial length as the permanent magnets. The concave portion defined by the outer wall, a stepped portion of the core, and a concave portion of the core defined by the support part bring about the position of the armature winding.